Intangible Assets

The gross carrying amount and accumulated amortization of our intangible assets, other than goodwill, were as follows:



	September 30, 2017							December 31, 2016
	Gross Assets		Accumulated Amortization			Net		Gross Assets		Accumulated Amortization			Net
	(in thousands)
Core-developed technology	$	425,198	$	(393,831	)	$	31,367	$	372,568	$	(354,878	)	$	17,690
Customer contracts and relationships	256,840		(193,317		)	63,523		224,467		(170,056		)	54,411
Trademarks and trade names	69,706		(65,537		)	4,169		61,785		(61,766		)	19
Other	11,582		(11,062		)	520		11,076		(11,045		)	31
Total intangible assets subject to amortization	$	763,326	$	(663,747	)	$	99,579	$	669,896	$	(597,745	)	$	72,151
In-process research and development	710		—			710		—		—			—
Total intangible assets	$	764,036	$	(663,747	)	$	100,289	$	669,896	$	(597,745	)	$	72,151

A summary of intangible asset activity is as follows:



	Nine Months Ended September 30,
	2017		2016
	(in thousands)
Beginning balance, intangible assets, gross	$	669,896	$	702,507
Intangible assets acquired	36,500		—
Effect of change in exchange rates	57,640		2,309
Ending balance, intangible assets, gross	$	764,036	$	704,816

On June 1, 2017, we completed the acquisition of Comverge Inc. by purchasing 100% of the voting stock of Peak Holding Corp., its parent company (Comverge). Intangible assets acquired in 2017 are based on the preliminary purchase price allocation relating to this acquisition. Comverge's intangible assets include in-process research and development, which is not amortized until such time as the associated development projects are completed. These projects are expected to be completed in the next three months. Refer to Note 16 for additional information regarding this acquisition.

Estimated future annual amortization expense is as follows:



Year Ending December 31,	Estimated Annual Amortization
	(in thousands)
2017 (amount remaining at September 30, 2017)	$	5,605
2018	19,065
2019	16,302
2020	14,003
2021	11,995
Beyond 2021	32,609
Total intangible assets subject to amortization	$	99,579